This invention relates generally to powder metallurgy and more specifically to sintered powder parts and articles. Powder metallurgy includes, but is not limited to, compacting, casting, and sintering including sintering with and/or without a liquid phase, and/or infiltration, and/or under a load and/or pressure. Some examples of sintered powder parts and articles that can be made according to this invention include structural, porous, friction, anti-friction, cutting, corrosion-, wear- and heat-resistant parts, and inserts. In particular the present invention relates to sintered powder abrasive and super-abrasive parts and articles such as tools for cutting, drilling, de-burning, grinding, dressing, polishing, lapping, honning, and roughening and workpieces and wear resistant items.
Powders and powder pre-forms are widely used in the manufacturing of numerous sintered powder products including but not limited to wear-resistant, abrasive and super-abrasive parts and/or articles and/or tools. Powders for manufacturing abrasive products are conventionally manufactured by mixing hard and/or super-hard particles with sinterable and/or fusible retaining powders with or without a binder additive. Some powder preforms are conventionally manufactured by compacting the powders at room temperature (so called xe2x80x9cgreenxe2x80x9d compacts or segments) or casting and curing a mixture of the powder and a liquid and/or paste binder.
In the abrasive industry, sintered abrasive parts and articles comprise hard particles that in most cases are randomly distributed in a sintered powder retaining matrix. Specifically, cutting segments for segmented tools (blades, drill bits, etc.) are manufactured by mixing hard particles with powders of the retaining matrix, then compacting the powder at room temperature into a xe2x80x9cgreenxe2x80x9d segment, then sintering the xe2x80x9cgreenxe2x80x9d segment or a plurality of xe2x80x9cgreenxe2x80x9d segments into an individual sintered segment or a plurality of individual sintered segments respectively. Sintering may include infiltration of other components or compaction. Such infiltration and/or compacting also can take place before and/or after sintering and/or after a preliminary sintering.
Typically the sinterable segments or parts such as abrasive cutting segments are sintered as individual or separate bodies. In other words, each segment is separated from another one by compacting means (punches/plungers) and/or solid dividers and/or walls. These compacting means and dividers are strong bodies (i.e., graphite or metallic parts) that are not supposed to be crushed or substantially deformed in the process of compacting and/or sintering the xe2x80x9cgreenxe2x80x9d segments. In the case of radiant or induction and/or microwave sintering, pressure and heat and/or an appropriate atmosphere can be provided by appropriate means. In the case of electro-resistant and/or electro-discharge sintering, electrical current and/or pressure are provided by and or delivered through the compacting means.
This is illustrated in FIG. 1 where sinterable powder segments 1 are placed in a sinter mold 5 containing punches 2 and a solid divider 3 and having opposing pressure plates 6. FIG. 2 illustrates a more efficient arrangement where the punches 2 also serve as dividers between the segments. In either case a plurality of individual sintered parts are produced.
These solid compacting means and/or dividers occupy a substantial part of the volume of the sinter mold, generally 50% to 70%, resulting in a lower efficiency and utilization of the sinter mold volume, e.g., only 50% to 30%.
Moreover, assembling numerous xe2x80x9cgreenxe2x80x9d segments and punches together into a sinter mold is a time consuming process. Mechanization and automation of this process is a challenging task. Also while disassembling this type of sinter mold after sintering, one has to deal with separating the sintered parts from the punches and collecting and cleaning numerous small and thin punches and dividers to prepare them for use in the next sintering step.
Producing the sintered parts by filling a powder instead of xe2x80x9cgreenxe2x80x9d compacts or segments into the cavities of the sinter mold that also includes compacting means and/or dividers is also known, but it results in an even lower efficiency of sintering because the powders have 1.5 to 5 times lower densities than the xe2x80x9cgreenxe2x80x9d segments and it also creates problems because of the difficulty in achieving a uniform distribution of the powder in the cavities.
As taught in WO 94/20252, published Sep. 15, 1994, it is also known to make sintered abrasive cutting segments by providing a sheet of sintered abrasive material and then cutting out the sheet into a plurality of cutting segments with a laser or the like.
In accordance with the present invention, a new and improved method is provided for making unique sintered products in the form of a sintered article or plate as well as to individual sintered segments or bodies that can be extracted from the sintered article by suitable extracting means, such as laser cutting, water jet cutting, electro-erosion cutting, abrasive cutting, edge tool cutting, and mechanical distraction (breakage).
More specifically, a method is provided for making a sintered article comprising providing a plurality of individual blocks of sinterable matrix material, arranging said blocks in abutting relationship to form an assembly of said blocks, wherein said assembly comprises a plurality of said blocks extending in at least one direction thereof, and sintering said assembly to form an integrated sintered article.
The method according to the invention thus is characterized by sintering together, for example, a plurality of powder preforms or green powder compacts made of a sinterable powder to form a sintered powder article.
In the process, the blocks or preforms are integrated with neighboring blocks during sintering to form the sintered article. Diffusion of the components of the blocks can promote their integration. The individual sintered segments or bodies, extracted from the sintered powder article, can or cannot correspond to the original green powder blocks or preforms.
Sintering in a sinter mold, preferably under pressure, can be used to obtain the sintered article. Sintering under pressure (so called xe2x80x9chot compactingxe2x80x9d) is a particularly
The assemblies can be of a variety of shapes including square, rectangular or round shapes and can optionally be provided with one or more through openings, such as a central opening.
In an advantageous embodiment of the invention a plurality of individual sintered powder segments or bodies are extracted from the sintered powder article. These individual sintered powder bodies can be used as articles or as parts of a larger article. They also can be of various one, two, or three dimensional shapes including, but not limited to, polygon, rectangular, square, round, cube, elliptical, cylindrical, pyramid, core, frustum cone, arc, nail, needle, pen, spiral and can have at least one indent and/or through opening.
If necessary, these extracted bodies can be readily joined or fixed to a carrier and/or to each other by gluing, welding, braising or by mechanical means such as locking or riveting, or by any combination thereof.
The blocks of sinterable matrix material can be made out of the same or different compositions. Therefore, depending on shape, size of the blocks, layout of the assembled blocks or the assembly and conditions of sintering, the resulting integrated sintered powder article can comprise a variety of compositions distributed through the article in a pre-determined, including but not limited to non-random, and desired manner. This enables the integrated sintered articles to be provided with unique characteristics of man-made material.
Furthermore, the assembly can comprise multiple layers, each layer comprising a plurality of the blocks so that individual bodies extracted from the same sintered assembly but from different parts thereof can have the same and/or different compositions and characteristics, and therefore different performance characteristics derived from the composition of the blocks, make-up of the assembly, presence of additional materials in the assembly, conditions of sintering and the pattern of extraction of the individual sintered bodies from the sintered article.
Depending upon the use of the final product, the sintered article and/or extracted individual bodies or members can be treated in a variety of ways including, but not limited to, thermal and/or pressure treatment (i.e., re-sintering in a vacuum or protective atmosphere, infiltration, impregnation, quenching, tempering, annealing, drawing, forging), mechanical and abrasive machining and plating (for example with a composition comprising hard particles such as diamonds) by, i.e., electrolytic and/or plasma methods.
Examples of applications for such products include, but are not limited to, laminated, layered or sandwiched composites and parts for construction, wear- and corrosion-resistant articles, breaks, heat absorbers, abrasive tools, edge tools, electrodes, electrical switches, insulators, porous filters, machine parts, etc.
Various manufacturing operations can be used to assemble the sinter mold load and the parts of the sinter mold or frame. This sinter mold load includes, but is not limited to blocks, at least partially assembled blocks and compacting means, such as punches, separators, insulators, side walls, etc. These manufacturing operations can also include, if needed, means for aligning, trimming, temporarily and permanent holding and assembling, moving, transporting and fastening the parts of the mold as well as the sinter mold load.
These operations may include labor (human hands), semi-automatic or automatic mechanisms, and robots that can form an assembly line. Adhesives, glues, fasteners, negative relative pressure (e.g., suction heads, vacuum), pressure, weight load, gravity, magnets (electrical, permanent, etc.), air/gas, heat, freezing, chilling, loading, pushing, pulling, friction and antifriction means, inserting, sliding, and any combination of these means with each other or with other means can be used. In the case of using pre-sintered or fully sintered powder preforms, they can be formed into an assembly of blocks by the use of soldering, brazing, infiltration, and welding.
The assembling of the blocks can take place completely within, at least partially within, or outside of the sinter mold or frame.
Therefore, any means for assembling and disassembling, transporting, moving, handling (i.e., lifting, sliding, turning, lowering, placing), inserting, aligning and trimming of a sinter mold load i.e., the components, which may include the blocks of sinterable material, at least partially assembled blocks, punches, separators, sintered articles and parts of the sinter mold/frame are within the scope of this invention.
It is also possible to introduce additional materials into the assembled block either in the process of or after the assembly thereof. These additional materials can be put between at least some of the blocks and/or layers of the blocks. These additional materials can provide reinforcement of the assembled blocks and/or sintered article and/or provide diffusion or diffusion enhancement components. Examples of additional materials include shims, foils, metallic and non-metallic materials, mesh type materials, sinterable materials, fusible and brazeable materials, materials exhibiting adhesive performance, liquid, paste, powder, cast powder, compacted (i.e., roll compacted) powder, semi-sintered, sintered powdered products and welded and brazed parts.
For a purpose of making abrasive and/or edge tools and wear-resistant parts, at least one of the blocks and/or the assembly of blocks can contain at least one type of a plurality of abrasive particles, and the resulting integrated sintered article can be used as an abrasive article or one or a plurality of individual sintered abrasive segments or abrasive cutting elements can be extracted from it by suitable extracting means, such as laser cutting, water jet cutting electro-erosion cutting, abrasive cutting, edge tool cutting, and mechanical distraction. These elements or segments can be of various shapes, including but not limited to, polygon, rectangular, square, round, elliptical disc, cylindrical, frustum cone, cube, pyramid, donut, sector, arc, pin, or spiral and can have at least one indent and/or through opening.
These articles can be used as grinding wheels, rotary dressers or the elements as the cutting and grinding segments of abrasive machining or cutting tools. Examples of individual extracted sintered abrasive segments for a tool include cutting members for cutting and/or edge tool, such as segments or tips for circular, chain, reciprocating and wire type cutting blades. Further examples of such tools include cutting, grinding, polishing, lapping, dressing, milling, roughening, chamfering, de-burning, gripping and friction tools. More specifically, the members can be used to form abrasive segmented cutting blades, abrasive segmented drill bits, continuous abrasive surfaces, or rims, segmented continuous abrasive surfaces or rims but with the segments tightly fixed, adjusted and/or joined to each other, e.g., by welding or braising to imitate a continuous and tools having combinations of such motions. Examples are face-grinding tools, cylindrical tools and other rotary tools, wheels, pencil wheels and conical tools.
Examples of materials that can be machined with these tools include sintered materials, ceramics, glass, wafer, semiconductor, metallic, non-metallic, fiber, graphite, carbon materials, hard metals, asphalt, natural or artificial stones, concrete, rocks, abrasive and super-abrasives, and floors made out of natural stone, artificial stone or concrete.
Preferably the extracted sintered abrasive elements or segments (i.e., the cutting and grinding cutting members) are shaped to be fixed to a tool carrier such as the core of a circular abrasive cutting blade or wheel. Prior to mounting on the carrier, the extracted sintered abrasive elements can be, if required, machined, re-cut, de-burred, trimmed and dressed as required.
Further, the plurality of abrasive particles may be randomly and/or non-randomly distributed in the sinterable matrix material of the blocks and/or in the assembly of the blocks, and therefore in the resulting sintered article, and at least in some of the acted elements. Non-random distribution can be provided by means of mesh type materials and/or tacky materials and/or by any other means such as but not limited to hard placement, CNC machines and any other placement and distribution devices including temporarily holding devices.
In addition, while some of the blocks can contain abrasive particles, others can contain no abrasive particles or a surface containing no abrasive particles to provide non-hard particle zones. In this way, bodies extracted from the sintered articles have at least one non-abrasive or hard particle zone enabling them to be more readily fixed to an abrasive tool carrier.
As disclosed above, these extracted bodies can be readily joined to a carrier such as an abrasive tool carrier, by means of gluing, welding, braising or mechanical means, i.e., locking or riveting, or by any combination of at least some of these methods.
The ability to obtain sintered extracted parts suitable for welding, (specifically, for laser, electron-beam and tig welding) and brazing (specifically, for induction and furnace braising) to a carrier is a particular advantage of this invention.
Considering, by a way of example, diamond-containing abrasive segments having a non-hard particle zone and/or surface can be readily integrated with a tool carrier because the absence of hard particles in the welding or braising zone makes this joining process more feasible and enhances the strength of the joint. These zone(s) (so called xe2x80x9cfeetxe2x80x9d) and/or surface(s) can also comprise material that is different from the matrix material used to retain the abrasive particles in the individual extracted body, that is more compatible for the purpose of joining, i.e., welding or braising, the material to the tool carrier. Further, the non-hard particle zone can comprise a few occasional hard particles or comprise hard particles of a concentration that is lower than the concentration of hard particles in other zones and/or on the surface of the extracted bodies as long as this concentration is low enough not to detrimentally effect the strength of the braise and/or weld seam.
Therefore this invention relates to a unique method for making integrated sintered articles that have a desirable and pre-determined distribution of components (e.g., hard particles), layers and compositions for optimization and high performance of the final products made from the articles as well as to individual elements or bodies extracted from the articles. This process is an efficient and economical way of manufacturing the articles which utilizes machinery and equipment that are readily available and widely used in the industry.